(a) Field of the Invention
The present invention pertains to a power amplifying circuit for use in amplifiers for driving speakers or like loads.
(b) Description of the Prior Art
Electric signals, especially musical signals, which require amplification have, in many cases, pulsive or steep waveshapes. However, power amplifying circuits are required to amplify the electric signals as faithfully as possible, i.e. without developing distortions due to clipping of the peak points of such pulsive waveshapes of the signals. To this end, conventional power amplifying circuits are designed so that the supply voltage which is to be applied to the power amplifying elements in the power amplifying circuit is fixed to a high voltage level relatively independent of the level of the electric signal to be amplified.
In case the level of the voltage which is supplied to the power amplifying elements is set to a high level, however, there entails the inconvenience that, in case, conversely, the electric signal is of a low level and has a gentle or blunt waveshape similar to a sinusoidal wave having a large energy, there arises an increased power loss and heat generation of the power amplifying elements. This would lead to destruction of these elements. An attempt to avoid this mode of destruction has required an uneconomically large-size heatsink.